Fuel cell system for an aircraft, method for operating a fuel cell system in an aircraft and aircraft with such a fuel cell system

A fuel cell system (2) comprises a first fuel cell unit (4) having a first fuel cell (8) and a second fuel cell (10), a second fuel cell unit (6) having a third fuel cell (54) and a fourth fuel cell (56), a hydrogen tank (36), an oxygen supply unit (38) and at least one air inlet (25). The first fuel cell unit (4) and the second fuel cell unit (6) are operable independently. All fuel cells (8, 10, 54, 56) are couplable with a hydrogen tank (36), while oxidant inlets (14) of the first fuel cell (8) and the fourth fuel cell (56) are couplable with the at least one air inlet (25) and wherein the oxidant inlets (14) of the second fuel cell (10) and the third fuel cell (54) are couplable with at least one oxidant supply unit (52). Said oxidant supply unit (52) is couplable with at least one of the oxygen supply unit (38) and the at least one air inlet (25). Exhaust outlets (20) of the first fuel cell (8) and of the fourth fuel cell (56) are couplable with at least one inert gas outlet (31, 33) and exhaust outlets (20) of the second fuel cell (10) and of the third fuel cell (54) are coupled with at least one exhaust switching unit (29). Said exhaust switching unit (29) is couplable with the at least one inert gas outlet (31, 33) and a water outlet (35). Thereby, a reliable and safe fuel cell system for providing power, emergency power, water, heat and inert gas is provided.